The present invention relates in general to the delivery of stents into a body lumen, such as a blood vessel, to maintain the patency thereof. More particularly, the present invention relates to an improved stent delivery system that can accurately deliver a self-expanding stent within a body lumen.
In a medical procedure known as percutaneous transluminal coronary angioplasty (PTCA), a balloon catheter is used to dilate the lumen of a coronary artery which has become narrowed or restricted due to the accumulation of atherosclerotic plaque along the artery wall. In the PTCA procedure, a balloon catheter is advanced through the vasculature to the stenosis and the balloon is inflated to radially compress the atherosclerotic plaque against the inside of the artery wall. The balloon is then deflated so that the dilation catheter can be removed and blood flow resumed through the dilated artery.
Occasionally, the inflation of the balloon within the artery lumen will dissect either the stenotic plaque or the intima of the blood vessel or both. After the balloon is deflated and removed, blood can flow between the arterial wall and the dissected lining thereby constricting the flow passage or causing a section of the dissected lining, commonly called an xe2x80x9cintimal flap,xe2x80x9d to be forced into the flow passageway. In the event of partial or total occlusion of an artery by a dissected arterial lining, the patient is put in an extremely dangerous situation requiring immediate medical attention.
Another problem which frequently arises after an angioplasty procedure is the appearance of a restenosis at or near the site of the treated artery. The restenosis may appear due to the accumulation of additional atherosclerotic plaque or may be the result of weakened arterial walls which have collapsed inward to restrict blood flow. When restenosis appears, the treated patient may require an additional angioplasty procedure or other treatment such as by-pass surgery, if an additional angioplasty procedure is not warranted.
Due to the problems caused by dissections of the arterial lining or the appearance of restenosis, much research has been performed on ways to maintain the patency of an artery after the angioplasty procedure is completed. In recent years, expandable endoprosthetic devices, commonly called xe2x80x9cstents,xe2x80x9d have gained widespread acceptance as a means to support the arterial walls and maintain the patency of a treated vessel. Stents are generally cylindrically shaped intravascular devices which are placed within a damaged artery to hold it open and maintain unimpeded blood flow. Stents prevent dissected arterial linings from occluding an artery by pressing the dissected tissue against the arterial wall until natural healing results in the re-securing of the dissected tissue to the arterial wall. Stents also prevent the appearance of restenosis in the treated vessel by supporting the weakened arterial walls.
Various means have been developed for delivering and implanting intravascular stents within a body lumen. One common method involves compressing or otherwise reducing the diameter of a self-expanding stent, mounting the compressed stent on the distal end of a delivery catheter, placing a tubular sheath over the stent to restrain the stent in the contracted condition, and advancing the catheter through the patient""s vasculature to the desired location. Once the stent is properly positioned, the stent is exposed by withdrawing the sheath proximally with respect to the stent, advancing the stent distally with respect to the sheath, or performing a combination of both. Once free from the sheath, the self-expanding stent expands against the arterial walls to thereby hold open the artery or other body lumen into which it is placed.
Other examples of stent delivery systems include U.S. Pat. No. 5,026,377 to Burton et al. Burton discloses an instrument for the deployment or retraction of a self expanding stent in a body canal, which comprises an elongated tubular outer sleeve having disposed therein an elongated core which is moveable relative to the sleeve and has a grip member formed at or near its distal end, which grip member is adapted to releasably hold a self-expanding stent within the outer sleeve. U.S. Pat. No. 5,190,058 to Jones et al. discloses a method of using a temporary stent catheter. The catheter comprises a catheter tube having a distal end and a proximal end; an elongated balloon inflatable by fluid pressure attached to the catheter tube near its distal end; a stent having a tubular configuration attached to the catheter tube near its distal end and surrounding the balloon; a pressurization device near the proximal end of the catheter tube for inflating and deflating the balloon, whereby the stent may be pressed against the wall of a blood vessel by the balloon and the balloon may be subsequently deflated; a restriction device near the proximal end of the catheter tube for maintaining the stent in an expanded condition and for subsequently effecting the radial contraction of the stent whereby it may be removed from the blood vessel.
U.S. Pat. No. 5,201,757 to Heyn et al. discloses an apparatus for deploying a radially self-expanding stent that includes proximal and distal sleeves respectively containing proximal and distal end portions of the stent in a reduced radius delivery configuration. Once the stent and sleeves are positioned at the intended fixation site, the sleeves are moved axially with respect to one another to permit radial self-expansion of the stent only over its medial region, while the sleeves continue to contain the axially outward regions of the stent. Upon sufficient movement of the sleeves axially relative to each other, the stent becomes totally free of the sleeves. U.S. Pat. No. 5,290,295 to Querals et al. discloses a tool for the intraluminal insertion and deployment of a tubular graft within a blood vessel, that is constructed from a flexible insertion shaft with a tapered distal end, a tubular sheath, a deployment slider and a safety locking tube.
U.S. Pat. No. 5,391,172 to Williams et al. discloses a stent delivery system with coaxial catheter handle. The catheter handle provides relative motion between the outer sheath of a stent delivery catheter and an underlying catheter, via a thumb switch, to enable the outer sheath to withdraw from over the underlying catheter and expose a vascular prosthesis.
U.S. Pat. No. 5,507,768 to Lau et al. discloses a stent delivery method and system that includes an elongated delivery sheath and a catheter disposed within an outer lumen of the sheath having an expandable member on its distal extremity. An expandable stent is mounted on the expandable member and the distal portion of the sheath tapers down and is tucked within an elastic cone during transport of the stent to a stenotic region. A manipulating device is provided on the proximal end of the delivery system to effect relative axial movement between the sheath and the catheter so as to expose the stent mounted on the expandable member on the catheter within a body lumen, such as a coronary artery, and allow the expansion of the stent by the expansion of the expandable member.
One of the difficulties with some prior stent deployment systems involves deploying the stent at the precise, desired location within the body lumen. Typically, a self-expanding stent is mounted on the distal end of a delivery catheter that is attached to a manipulator handle outside the patient""s body. The stent is deployed by actuating a mechanism on the manipulator handle, such as a thumb plate, which is hand operated by the physician. When the thumb plate is withdrawn proximally relative to the manipulator handle, the sheath is withdrawn proximally relative to the catheter and stent.
Problems can arise when the sheath is retracted proximally by the application of a pulling force. The friction between both the stent and the sheath and the catheter and the sheath must be overcome by the pulling force in order for the stent to be deployed. The tensile force exerted on the outer sheath will be opposed by an equivalent compressive force exerted on the catheter. When compression of the catheter occurs, the sheath may not retract relative to the stent.
Alternatively, the sheath may retract after the catheter has already been compressed a certain amount. Consequently, the stent may not be deployed precisely in the desired location. Physicians have very little tolerance when it comes to inaccuracy of stent placement. A placement error of only millimeters is often considered to be intolerable. A poorly placed stent may do more harm than good and can be very difficult to retrieve once deployed. Therefore, it is critical to position the stent accurately on the first attempt.
A metal hypotube can be used throughout the length of the catheter to reinforce the catheter and increase the compression resistance of the catheter. However, the use of a hypotube at the distal end of the catheter can provide for a device that is generally not flexible enough to properly navigate through tortuous areas of the vasculature. Furthermore, some prior art attempts have produced catheters that are bulky and thick. These configurations may be prone to dislodging arterial plaque and are not ideal for navigation through a tortuous vasculature.
What has been needed and heretofore unavailable is a stent deployment system for self-expanding stents that provides a means to prevent unwanted movement of the stent and to provide greater accuracy of stent placement within a body lumen. The device should be highly resistant to compressive forces yet maintain enough flexibility for navigation through the highly tortuous vasculature. Additionally, the system should be relatively easy to use and manufacture. The present invention satisfies these needs and others.
As used herein, the terms xe2x80x9cproximal,xe2x80x9d xe2x80x9cproximallyxe2x80x9d and xe2x80x9cproximal directionxe2x80x9d when used with respect to the invention are intended to mean moving away from or out of the patient, and the terms xe2x80x9cdistal,xe2x80x9d xe2x80x9cdistallyxe2x80x9d and xe2x80x9cdistal directionxe2x80x9d when used with respect to the invention are intended to mean moving toward or into the patient. These definitions will apply with reference to apparatus, such as catheters, guide wires, stents and the like.
The invention provides for a stent deployment system for delivering a self-expanding stent within a body lumen. The system provides for both resistance to longitudinal compression while at the same time retains adequate flexibility for navigation through a tortuous vasculature.
In one aspect of the invention, there is provided a stent deployment system for delivery of a self-expanding stent within a body lumen. The system includes a delivery assembly and a guide catheter. The delivery assembly includes an inner tubular member. The distal end of the inner tubular member is configured to receive over an exterior thereof the self-expanding stent. At least a portion of the inner tubular member includes a first reinforcing element connected thereto. The first reinforcing element provides longitudinal compression resistance for the inner tubular member, while allowing for flexibility for navigation through a tortuous vasculature. The delivery assembly also includes an elongated sheath formed with a lumen to slidably receive the inner tubular member. The guide catheter is formed with a lumen for receiving the delivery assembly therein.
The stent delivery system can be used to accurately deliver a stent to a desired location within a patient""s vasculature system or other body lumen by preventing unwanted axial motion of the self-expanding stent during the deployment process. The stent delivery system is safe, easy-to-use and can be quickly and easily removed after the stent has been deployed. The present invention is designed primarily for use in the carotid arteries; however, the system also can be used to treat other vessels. Other features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.